Operation of a hvac system using a combined hydronic and force air system

ABSTRACT

A method for cooling or heating a building is provided. An air flow can be created in an air duct and the air flow can be cooled or heated by an air conditioning system or furnace. The cooled or heated air flow can then pass through a heat exchanger connected to a radiant heating loop running through a floor or slab with a liquid circulating through them. When the airflow is being cooled or heated by the air conditioning system or furnace, the air flow will alter the temperature of the liquid circulating through the heat exchanger herefore the temperature of the slab. When the temperature of the slab varies from the temperature of the building, liquid that has been circulated through the radiant heating loop can be used to alter the temperature of the air flow passing through the heat exchanger.

This invention is in the field of heating and/or cooling systems andmore particular relates to methods of operating a radiant heating systemto cool a cement floor or slab and then using this cooled floor or slabto cool an air flow.

BACKGROUND

Many buildings, especially residential buildings, use cooling systems tocool an air flow that is then passed into the building to cool the airin the building. Typically, these cooling systems comprise an airconditioner condenser and evaporator operating in conjunction to coolthe air flow. An air flow is passed through the evaporator to cool theair flow and then it is routed through an air duct into the buildingwhere cooled air flow enters the building and cools the air in thebuilding.

However, these systems use electricity to operate the air conditionercondenser. In some areas electrical power is subject to varying ratesthroughout the day, with consumers being charged higher rates forelectricity used during peak hours. Other times, it is simply desirablenot to constantly use electricity to power the air conditionercondenser.

Radiant heating systems are also now commonly used in buildings. Thesesystems provide heat by having heated fluid circulated through them in aseries of conduits or a heating loop that is provided in a cement flooror slab. Heat from the heating fluid circulating through the radiantheating loop is radiated to the surrounding floor or slab, heating thefloor or slab and thereby radiating heat to the surrounding area.

There are also systems that can transfer heat between an air flowpassing through the air duct of a forced air furnace and a cement flooror slab. A system such as this is shown in U.S. Pat. No. 7,410,104 toMacPherson the inventor of the current system and method.

SUMMARY

In a first aspect, a method of cooling a building is provided. Themethod comprises: using a blower to create an air flow through an airduct in the building, the air flow to be directed into the building;providing an air conditioning system with an evaporator in the air duct,the air conditioning system operative to cool the air flow in the airduct as it passes the evaporator, providing a radiant heating apparatuscomprising: an air-to-fluid heat exchanger in the air duct downstreamfrom the evaporator of the air condition system; a radiant heating loopoperatively connected to the air-to-fluid heat exchanger and provided ina thermal store in the building; a liquid circulating through theair-to-fluid heat exchanger and the radiant heating loop. The airconditioning system and the radiant heating system can be first operatedin a first state by cooling the air flow in the air duct using the airconditioning system and passing the cooled air flow through theair-to-fluid heat exchanger before the air flow is discharged into thebuilding so that the cooled air flow cools the liquid circulatingthrough the air-to-fluid heat exchanger and the cooled liquid beingcirculated through the radiant heating loop cools thermal store. Thenwhen the thermal store is cooler than an ambient temperature in thebuilding, the air condition system and the radiant heating system can beoperated in a second state by turning off the air conditioning system sothat the air flow through the air duct is at substantially the ambienttemperature, circulating the liquid cooled by the thermal store throughthe radiant heating apparatus and cooling the air flow by passing theair flow through the air-to-fluid heat exchanger as the cooled liquidpasses through the air-to-fluid heat exchanger before discharging theair flow into the building.

In a second aspect, a method of heating a building is provided. Themethod comprises: providing a forced air furnace with a blower connectedto an air duct in the building; using the blower to create an air flowthrough the air duct in the building, the air flow to be directed intothe building; providing a radiant heating apparatus comprising: anair-to-fluid heat exchanger in the air duct downstream from theevaporator of the air condition system; a radiant heating loopoperatively connected to the air-to-fluid heat exchanger and provided ina thermal store in the building; a liquid circulating through theair-to-fluid heat exchanger and the radiant heating loop. The method canoperate the forced air furnace and the radiant heating system in a firststate by heating the air flow in the air duct using the forced airfurance and passing the heated air flow through the air-to-fluid heatexchanger before the air flow is discharged into the building, theheated air flow heating the liquid circulating through the air-to-fluidheat exchanger and the heated liquid being circulated through theradiant heating loop to heat the thermal store. When the thermal storeis warmer than an ambient temperature in the building, the method canoperate the forced air furnace and the radiant heating system in asecond state by turning off the forced air furnace so that the air flowthrough the air duct is at substantially the ambient temperature,circulating the liquid heated by the thermal store through the radiantheating apparatus and heating the air flow by passing the air flowthrough the air-to-fluid heat exchanger as the heated liquid passesthrough the air-to-fluid heat exchanger before discharging the air flowinto the building.

In a third aspect, a controller for controlling an air conditioningsystem and radiant heating apparatus in a building is provided. The airconditioning system comprises: an air conditioning condenser and anevaporator in a duct leading into the building, The radiant heatingapparatus comprising an air-to-fluid heat exchanger provided in the ductand operatively connected to a radiant heating loop in a thermal storein the building; and a pump operative to circulate a liquid through theair-to-fluid heat exchanger and the radiant heating loop. The controllercomprises: a processor; and a memory containing program instructions.The processor operative to in response to the program instructions:operate the air conditioning system and the radiant heating system in afirst state by using the air conditioning system to cool an air flow inthe air duct and pass the cooled air flow through the air-to-fluid heatexchanger before the air flow is discharged into the building andoperate the pump to circulate the liquid through the radiant heatingapparatus so that the cooled air flow cools the liquid circulatingthrough the air-to-fluid heat exchanger and the cooled liquid beingcirculated through the radiant heating loop cools the thermal store; andwhen the thermal store is cooler than an ambient temperature in thebuilding, operate the air conditioning system and the radiant heatingsystem in a second state by turning off the air conditioning system sothat the air flow through the air duct is at substantially an ambienttemperature, and having the pump circulate the liquid cooled by thethermal store through the radiant heating apparatus to cool the air flowas the air flow passes through the air-to-fluid heat exchanger beforedischarging the air flow into the building.

DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention is described below withreference to the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a cooling system; and

FIG. 2 is a state diagram of the modes of operating a cooling system asshown in FIG. 1.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 is a schematic illustration of a system 1 for heating and coolinga building. The system 1 can include a radiant heating apparatus 10 thatcan transfer heat between an air flow passing through an air duct 25 anda cement floor or slab. The radiant heating apparatus 10 can include: anair-to-fluid heat exchanger 100; a fluid supply conduit 120; a fluidreturn conduit 130; a pump 140; and a radiant heating loop 150. Theradiant heating apparatus 10 can be installed in conjunction with aforced air furnace 20 and a blower 27 that is connected to an air duct25.

The forced air furnace 20 can be any forced air furnace as commonlyknown by those skilled in the art, such as for example a gas furnace,oil furnace, heat pump, packaged outdoor heating/cooling units, etc. Theforced air furnace 20 will typically be the primary source of heatingand cooling for the building and will be connected to the air duct 25.The blower 27 is used in conjunction with the forced air furnace 20 toforce air through the forced air furnace 20 and out into the air duct25. The air duct 25 is operative to distribute an air flow passingthrough the air duct 25 throughout the building by eventuallydischarging the air flow into the building. The forced air furnace 20will typically be controlled with a furnace thermostat that is locatedin the main occupied heated area. The furnace thermostat will be inelectrical communication with the forced air furnace 20.

In addition to the forced air furnace 20, an air conditioning system canbe provided to work in conjunction with the forced air furnace 20 andthe air duct 25. The air conditioning system can be used to cool anunheated air flow passing through the air duct 25. Typically, this isdone with the use of an air conditioning condenser 30 and an evaporator35. The air conditioning condenser 30 is typically provided outside thefurnace and the evaporator is installed in the air duct 25 downstreamfrom the forced air furnace 25. The blower 27 can be used to create anair flow passing through the air duct 25 while the forced air furnace 25is not on and not being used to heat the air flow. The air flow can bedirected through the evaporator 35 where the air flow is cooled beforeit is passed through the air duct 25 and eventually out into thebuilding the system is installed in.

The air-to-fluid heat exchanger 100 can be any air-to-fluid heatexchanger that is operative to transfer heat between the air flow in theair duct 25 and liquid circulating through the air-to-fluid heatexchanger 100. The air-to-fluid heat exchanger 100 can have an inputconnection 105 for liquid to be circulated into the air-to-fluid heatexchanger 100 and an output connection 110 for liquid to be circulatedout of the air-to-fluid heat exchanger 100 after the liquid hascompletely circulated through the air-to-fluid heat exchanger 100.

The liquid that is circulated through the radiant heating apparatus 10can be any liquid that is operative to store and transfer heat throughthe radiant heating apparatus 10, but would typically be water, treatedwater, or glycol.

The fluid supply conduit 120 can have a first end 122 and a second end126. The first end 122 of the fluid supply conduit 120 is connectable tothe output connection 105 of the air-to-fluid heat exchanger 100 and thesecond end 126 of the fluid supply conduit 120 is connectable to theradiant heating loop 150.

The fluid return conduit 130 has a first end 132 and a second end 136.The first end 132 of the fluid return conduit 130 is connectable to theinput connection 110 of the air-to-fluid heat exchanger 100 and thesecond end 136 of the fluid return conduit 130 is connectable to theradiant heating loop 150.

The pump 140 can be any pump that is operative to circulate the liquidthrough the radiant heating apparatus 10. The pump 140 is illustrated inFIG. 1 as connected to the fluid supply conduit 120, however, someoneskilled in the art will readily appreciate that the pump 140 could beincorporated into the radiant heating apparatus 10 in many locationsincluding in the return supply conduit 130.

The radiant heating loop 10 can be a series of tubing or other conduitsthrough which the liquid will circulate and heat or cool the area inproximity to the radiant heating loop 150. Typically, the radiantheating loop 150 will be in-floor or in-slab heating system. Thesein-floor or in-slab heating systems typically comprise a plurality ofplastic tubing that is either cast into a cement floor of newconstruction or cast into a concrete slurry that is topped over anexisting slab. The cement or other material that makes up the floor orslab the radiant heating loop 150 is embedded in can form a thermalstore 260 storing up either heat or staying cool as a result of heattransfer between the radiant heating loop 150 and the thermal store 160.

A controller 40 can be provided for controlling the operation of the airconditioning system, the forced air furnace 20, the blower 20 and thepump 140 in the radiant heating apparatus 10. The controller 40 caninclude a processor 42 and a memory 44 with program instructions 46saved in the memory 44. The processor 42 is operative to execute theinstructions 46 in the memory 44 to control the air conditioning system,the forced air furnace 20, the blower 20 and the pump 140.

The controller 40 can include a temperature sensor 52 for measuring theambient temperature of the air in the building and in one aspect, canhave a temperature sensor 50 operably connected to it for measuring thetemperature of the thermal store 160.

In operation, the air-to-fluid heat exchanger 100 is located within theair duct 25. When an air flow is directed through the air-to-fluid heatexchanger 100 by the blower 27, this air flow can cool the liquidpassing through the air-to-fluid heat exchanger 100 if the air flow iscooler than the liquid in the air-to-fluid heat exchanger 100. Forexample, if the air conditioner condenser 30 and evaporator 35 are beingused to cool the air flow flowing through the air duct 25, the air flowcan be cooler than the liquid passing through the air-to-fluid heatexchanger 100 which in turn will cool the liquid passing through theair-to-fluid heat exchanger 100. Alternatively, the air flow can heatthe fluid passing through the air-to-fluid heat exchanger 100,increasing the temperature of this liquid, if the air flow has a greatertemperature than the fluid in the air-to-fluid heat exchanger 100. Thiscould occur when the forced air furnace 20 is being used to heat the airflow being directed into the air duct 25.

Once the liquid passes through the air-to-fluid heat exchanger 100, theliquid can then pass out of the output connection 110 through the firstend 122 of the fluid supply conduit 120, into the fluid supply conduit120, through the fluid supply conduit 120 and into the radiant heatingloop 150. The liquid can then circulate through the radiant heating loop150. If the fluid has been cooled by a colder air flow passing throughthe air-to-fluid heat exchanger 100, then this cooled liquid can coolthe thermal store 160 surrounding the radiant heating loop 150 andeventually the room of the building above the thermal store 160. If theliquid has been heated by a warmer air flow passing through theair-to-fluid heat exchanger 100, then this heated liquid can heat thethermal store 160 that the radiant heating loop 150 is provided in andthis heated thermal store 160 can subsequently heat the portion of thebuilding above the thermal store 160.

Once the liquid has circulated through the radiant heating loop 150, theheating liquid will then pass into the fluid return conduit 130 and backinto the air-to-fluid heat exchanger 100, where the temperature of thefluid can once again be changed by the air flowing through the air duct25.

The radiant heating apparatus 10 can also be operated to cool airflowing through the air duct 25 when the thermal store 160 surroundingthe radiant heating loop 150 is below the ambient temperature. Theblower 27 can be used to blow air that has neither been heated by theforced air furnace 25 or the air condition system through the air duct25. The result is an air flow that is at approximately ambienttemperature. While this air flow is being forced through the air duct 25by the blower 27, the pump 140 can be started and the liquid in theradiant heating apparatus 10 circulated. The thermal store 160surrounding the radiant heating loop 150 can cool the liquid beingcirculated through the radiant heating loop 150. This liquid will thenbe circulated through the air-to-fluid heat exchanger 100. The cooledfluid circulating through the air-to-fluid heat exchanger 100 will drawsome of the heat from the air flow coming into contact with theair-to-fluid heat exchanger 100, cooling the air flow passing throughthe air-to-fluid exchanger 100. This cooled air flow will then bedispersed throughout the building via the ducting connected to theforced air furnace 20.

The system 1 can be operated so that the air conditioning system is usedto cool an air flow that will cool the air in the building. This cooledair flow will also be used to cool the liquid circulating through theair-to-fluid heat exchanger 100 which in turn will lower the temperatureof the cement floor/slab making up the thermal store 160 surrounding theradiant heating loop 150. When the thermal store 160 has a temperaturebelow the ambient temperature, the air conditioning system can bestopped so that the air flow is no longer cooled by the air conditioningsystem and the fluid that is circulating through the apparatus will nowbe cooled by the colder thermal store 160 and can be used to cool an airflow passing through the air duct 25. In this manner, the system 1 canbe run at certain times to cool the thermal store 160 while cooling thetemperature inside the building and at other times the system 1 can beoperated so that the cooled thermal store 160 can supply the coolingdesired for the building.

FIG. 2 illustrates a state diagram illustrating two states of operationfor the system 1. At state 210 the system 1 uses the air conditioningsystem to cool an air flow passing through the air duct 25 and thethermal store 160 formed from the cement floor or slab. At step 220 thesystem 1 reverses and the cooling is provided by the cooled thermalstore 160, which is used to cool fluid in the radiant heating apparatus10 and subsequently an air flow passing through the air duct 25.

At state 210 the radiant heating apparatus 10 can be used to cool thebuilding by cooling the concrete or other material forming the thermalstore 160 surrounding the radiant heating loop 150. An air stream can beforced through the air ducts 25 using the blower 27. This air stream canbe cooled by the air conditioning condenser 30 and the evaporator 35, bypassing the air stream through the evaporator 35 before the cooled airflow is routed through the air duct 25 and through the air-to-fluid heatexchanger 100. Liquid that is being circulated through the radiantheating apparatus 10 will circulate through the air-to-fluid heatexchanger 100 where it will be cooled by the cooled air flow before itis routed to the radiant heating loop 150 running through the thermalstore 160. The cooled liquid passing through the radiant heating loop150 will cool the thermal store 160 and subsequently the area above thethermal store 160. At the same time the building is being cooled by thecooled thermal store 160, the cooled air flow will be routed through theair duct 25 and into the building as well.

As the liquid passing through the radiant heating apparatus 10 continuesto cool the thermal store 160 surrounding the radiant heating loop 150,the thermal store 160 can be cooled to a temperature below the ambienttemperature in the building. In some cases, the thermal store 160 maytypically maintain a temperature that is below the ambient temperaturein the building without it having to be cooled. This can occur when thethermal store 160 is the cement floor of a basement or cement slab thatis in contact with a ground surface that tends to be cooler than theambient air temperatures in the building. As long as the system 1 isbeing operated in state 210, the thermal store 160 will continue to becooled.

In state 220, the air conditioning system is turned off while anuncooled air flow continues to be forced through the air duct 25 by theblower 27 and the cooled thermal store 160 is used to cool the liquid inthe air to fluid heat exchanger 100 which in turn will cool this airflow passing through the air duct 25. If the temperature of the thermalstore 160 is below the ambient temperature of the air in the building,the air flow passing through the air duct 25 can be stopped being cooledby the air conditioning condenser 30 and the evaporator 35 while theblower 27 maintains an air flow through the air duct 25 and through theair-to-fluid heat exchanger 100. The liquid that is being circulatedthrough the radiant heating apparatus 10 will still circulate throughthe air-to-fluid heat exchanger 100. However, rather than the cooled airflow having a temperature below the liquid passing through theair-to-fluid heat exchanger 100, and therefore cooling the liquid (asthe system 1 operates in state 210), the uncooled air stream can have atemperature greater than the liquid passing through the air-to-fluidheat exchanger 100 and the liquid passing through the air-to-fluid heatexchanger 100 can then cool the uncooled air flow.

Cooling the air flow will cause the temperature of the liquid passingthrough the air-to-fluid heat exchanger 100 to be increased and theliquid, after passing through the air-to-fluid heat exchanger 100, willbe circulated through the radiant heating loop 150. Where in state 210,the liquid passing through the radiant heating loop 150 cools thesurrounding thermal store 160, now in state 220 the liquid is cooled bythe colder thermal store 160. After this cooled liquid exits the radiantheating loop 150, the cooled liquid can be recirculated through theair-to-fluid intercooler 100 to cool the air flow passing through theair-to-fluid heat exchanger 100 before being once again recirculated tothe radiant heating loop 150 to be cooled again.

State 220 can continue with the liquid being cooled by the coolerthermal store 160 and recirculated through the air-to-fluid intercooler100 to cool a warmer air stream passing through the air duct 25 untilthe temperature of the thermal store 160 becomes close enough to theambient temperature to make the cooling ineffective.

The operation of the system 1 can be changed from the first state 210 tothe second stage 220 in response to a first trigger event 230. Thisfirst trigger event 230 could be as simple as a person manuallyswitching the operation of the system 1 from state 210 to state 220.However, in another aspect, the first trigger event 230 could be thetemperature of the thermal store 160 reaching a desired temperaturebelow the ambient temperature. This temperature would indicate that thethermal store 160 is sufficiently cool so that the thermal store 160 canbe used to cool the liquid in the radiant heating apparatus 100 and inturn the liquid can cool an air flow in the air duct 25.

If the controller 40 is used to control the system 1, the controller canuse the temperature sensor 50 to measure the temperature of the thermalstore 160 and when the thermal store 160 is cooled to the desiredtemperature, the controller 40 can stop the operation of the aircondition system while continuing to run the pump 140 and circulateliquid through the radiant heating apparatus 10.

In a further aspect, the first trigger event 230 could be the increasingof the electrical rates at a certain time of day causing the cost to runthe air conditioner condenser 30 and the evaporator 35 to be increased.By using this as a first trigger event 230, the system 1 could be usedto allow the air conditioning condenser 30 and the evaporator 35 to berun while electrical charges are at a lower rate and cool the thermalstore 160. Then when electrical rates increase during a day, such as atpeak electrical usage times where electrical rates are increased by theelectricity provider, the first trigger event 230 can occur and thesystem 1 can move into state 220 and the air conditioner condenser 30and the evaporator 35 can be turned off to reduce electrical consumptionand the cooled thermal store 260 used to cool the air flow and thebuilding.

If the controller 40 is used to operate the system 1, the controller 40can store the utility rates throughout the day in the memory 44 and whenthe utility rates are increased during the day, the controller 40 canturn off the air conditioning system while the pumps 140 continue tooperate to circulate liquid through the radiant heating apparatus 10.

In a further aspect, the trigger could be the receiving of a signal froman electrical utility provider. The controller 40 could receive thesignal from the utility provider and switch operation of the system 1from the first state 210 to the second state 220 by turning of the airconditioning system (the air conditioning condenser 30 and theevaporator 35) while allowing the pumps 140 to keep running to continuecirculating liquid through the radiant heating apparatus 10. In thismanner, the utility provider could reduce the power demands on theirelectrical generation equipment at desired times even if they do nothave varying electrical rates by simply sending out the signal tovarious systems and having them shut down the air conditioning systemsto reduce the power demands on their electrical generation equipment.This could be done at times of peak usage, etc.

A second trigger event 240 can be used to change the operating state ofthe system 1 from the second state 220, with the liquid being cooled bythe cooler thermal store 160 which is then used to cool the air flow inthe air duct 25, to the first state 210, with air conditioning systembeing once again used to supply a cooled air flow to the building andcool the thermal store 160. The second trigger event 240 could simply bea user changing the operation of the system 1 when desired.

In another aspect, the second trigger event 240 could be the temperatureof the thermal store 260 increasing to a point where the temperature ofthe thermal store 260 is no longer low enough relative to the ambienttemperature to adequately cool the air flow passing through the air duct25.

If the controller 40 is used to control the system 1, when thetemperature reading taken by the controller 40 of the ambienttemperature of the air in the building using temperature sensor 52reaches a lower value sufficiently close to the temperature of thethermal store 160 measured by the temperature sensor 50, the controller40 can switch the state of operation of the system 1 to the second firststate 210 by once again turning on the air conditioning condenser 30 andthe evaporator 35.

In a further aspect, the second trigger event 240 could also be anelectrical rate being decreased at a certain time of day. Allowing theair conditioning system 1 to once again be run during a time whenelectric rates are lower.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous changes and modifications willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly, all such suitable changes or modificationsin structure or operation which may be resorted to are intended to fallwithin the scope of the claimed invention.

1. A method of cooling a building, the method comprising: using a blowerto create an air flow through an air duct in the building, the air flowto be directed into the building; providing an air conditioning systemwith an evaporator in the air duct, the air conditioning systemoperative to cool the air flow in the air duct as the air flow passesthe evaporator; providing a radiant heating apparatus comprising: anair-to-fluid heat exchanger in the air duct downstream from theevaporator of the air condition system; a radiant heating loopoperatively connected to the air-to-fluid heat exchanger and provided ina thermal store in the building; a liquid circulating through theair-to-fluid heat exchanger and the radiant heating loop, operating theair conditioning system and the radiant heating system in a first stateby cooling the air flow in the air duct using the air conditioningsystem and passing the cooled air flow through the air-to-fluid heatexchanger before the air flow is discharged into the building so thatthe cooled air flow cools the liquid circulating through theair-to-fluid heat exchanger and the cooled liquid being circulatedthrough the radiant heating loop cools thermal store; and when thethermal store is cooler than an ambient temperature in the building,operating the air condition system and the radiant heating system in asecond state by turning off the air conditioning system so that the airflow through the air duct is at substantially the ambient temperature,circulating the liquid cooled by the thermal store through the radiantheating apparatus and cooling the air flow by passing the air flowthrough the air-to-fluid heat exchanger as the cooled liquid passesthrough the air-to-fluid heat exchanger before discharging the air flowinto the building.
 2. The method of claim 1 wherein the liquid iscirculated through the radiant heating apparatus using a pump.
 3. Themethod of claim 1 wherein the liquid is at least one of water andglycol.
 4. The method of claim 1 wherein the thermal store is one of afloor and a slab.
 5. The method of claim 1 wherein the air conditioningsystem and the radiant heating system switch from operating in the firststate to operating in the second state when the temperature of thethermal store reaches a desired temperature below the ambienttemperature in the building.
 6. The method of claim 1 wherein the airconditioning system and the radiant heating system switch from operatingin the first state to operating in the second state when the electricalrates reach a predetermined amount.
 7. The method of claim 1 wherein theair conditioning system and the radiant heating system switch fromoperating in the first state to operating in the second state when asignal is received from a utility provider.
 8. The method of claim 1wherein the air conditioning system and the radiant heating systemswitch from operating in the second state to operating in the firststate when a temperature differential between the temperature of thethermal store and the ambient temperature of the building reaches apredetermined value.
 9. A method of heating a building, the methodcomprising: providing a forced air furnace with a blower connected to anair duct in the building; using the blower to create an air flow throughthe air duct in the building, the air flow to be directed into thebuilding; providing a radiant heating apparatus comprising: anair-to-fluid heat exchanger in the air duct downstream from theevaporator of the air condition system; a radiant heating loopoperatively connected to the air-to-fluid heat exchanger and provided ina thermal store in the building; a liquid circulating through theair-to-fluid heat exchanger and the radiant heating loop, operating theforced air furnace and the radiant heating system in a first state byheating the air flow in the air duct using the forced air furnace andpassing the heated air flow through the air-to-fluid heat exchangerbefore the air flow is discharged into the building, the heated air flowheating the liquid circulating through the air-to-fluid heat exchangerand the heated liquid being circulated through the radiant heating loopto heat the thermal store; and when the thermal store is warmer than anambient temperature in the building, operating the forced air furnaceand the radiant heating system in a second state by turning off theforced air furnace so that the air flow through the air duct is atsubstantially the ambient temperature, circulating the liquid heated bythe thermal store through the radiant heating apparatus and heating theair flow by passing the air flow through the air-to-fluid heat exchangeras the heated liquid passes through the air-to-fluid heat exchangerbefore discharging the air flow into the building.
 10. The method ofclaim 9 wherein the liquid is circulated through the radiant heatingapparatus using a pump.
 11. The method of claim 9 wherein the liquid isat least one of water and glycol.
 12. The method of claim 9 wherein thethermal store is one of a floor and a slab.
 13. The method of claim 9wherein the forced air furnace and the radiant heating system switchfrom operating in the first state to operating in the second state whenthe temperature of the thermal store reaches a desired temperature abovethe ambient temperature in the building.
 14. A controller forcontrolling an air conditioning system and radiant heating apparatus ina building, the air conditioning system comprising: an air conditioningcondenser and an evaporator in a duct leading into the building, theradiant heating apparatus comprising an air-to-fluid heat exchangerprovided in the duct and operatively connected to a radiant heating loopin a thermal store in the building; and a pump operative to circulate aliquid through the air-to-fluid heat exchanger and the radiant heatingloop, the controller comprising: a processor, and a memory containingprogram instructions, the processor operative to in response to theprogram instructions: operate the air conditioning system and theradiant heating system in a first state by using the air conditioningsystem to cool an air flow in the air duct and pass the cooled air flowthrough the air-to-fluid heat exchanger before the air flow isdischarged into the building and operate the pump to circulate theliquid through the radiant heating apparatus so that the cooled air flowcools the liquid circulating through the air-to-fluid heat exchanger andthe cooled liquid being circulated through the radiant heating loopcools the thermal store; and when the thermal store is cooler than anambient temperature in the building, operate the air conditioning systemand the radiant heating system in a second state by turning off the airconditioning system so that the air flow through the air duct is atsubstantially an ambient temperature, and having the pump circulate theliquid cooled by the thermal store through the radiant heating apparatusto cool the air flow as the air flow passes through the air-to-fluidheat exchanger before discharging the air flow into the building. 15.The controller of claim 14 wherein the controller is operative tomeasure the ambient temperature in the building and a temperature of thethermal store and wherein the controller switches from operating the airconditioning system and the radiant heating system in the first state tothe second state when the controller measures a temperature of thethermal store that is a desired temperature below an ambient temperaturein the building.
 16. The controller of claim 14 wherein the controllerswitches from operating the air conditioning system and the radiantheating system in the first state to the second state when theelectrical rates reach a predetermined amount.
 17. The controller ofclaim 14 wherein the controller switches from operating the airconditioning system and the radiant heating system in the first state tothe second state when the controller receives a signal from a utilityprovider.
 18. The controller of claim 15 wherein the controller switchesfrom operating the air conditioning system and the radiant heatingsystem in the second state to the first state when a temperaturedifferential between the temperature of the thermal store and theambient temperature of the building reaches a predetermined value.